Doesn't PipelinDB limit you to postgres' scaling capabilities?
PipelineDB also offers a clustering extension for large workloads (see: http://enterprise.pipelinedb.com/docs/)
But in terms of ad hoc, exploratory analytics workloads, yes - the scaling limitations would be the same, since for ad hoc, exploratory analytics PipelineDB and PostgreSQL are the same. But with that said, the processed, aggregated data that gets stored is generally much smaller than large volumes of granular data, so there is much less data to comb through with PipelineDB.